Fog reduction in photographic silver halide emulsions



h the like; aryl such as phenyl, toluyl, naphthyl, and the formula whichwe have foundto be eflfective are:

United States lC Patented och 1,

S-(p-carboxyethyl)-cysteine and its sodium, potassium;

ammonium, silver or amine salt.

2,955,036 7 S-(v-carboxypropyl)-cysteine and the methyl, ethyl or Qphenyl esters thereof. o FOG XE EE E &%%% SILVERS-carboxymethyl-cysteine hydrochloride Fritz Dersch and Millet R. DeAngelus, Binghamton, B50200C'?H'GHZ SCHPOQOCZHE N.Y., assignors toGeneral Aniline & Film Corpora- NH, 7 New York a corporation of Delaware S-carbethoxymethyl-cysteine ethyl ester No Drawing. Filed Apr.25, 1958, Ser. No. 730,794 7 S-(p-carbethoxymethyl)-cysteine ethyl ester"8 Claims. (Cl. 96-66) 10 nooc cncnvs cnrooon NHO C-C5H5N-benzoyl-S-carboxymethyl-cysteine use of antifo in J The presentinvention relates to the g g H3O QOO CHGHZ S CHQ C O 0 CH3 andstabilizing agents for photographic silver halide emulsions and, moreparticularly, to the employment of NHQQCGHE I s carboxy-alkyl-cysteines,their salts and esters for such benzoyl cai-homethoxymethyhoysteiho m hl P P ester. -It is recognized that'light sensitive emulsions such as Nbenzoyl s oarboethoxymethyhoysteiho ethyl ester} gelatino silver halideemulsions have a tendency to fog. 2o N aoetyhgoarhothoxymothyhoystoiiieh l ester, 7 The feg may be caused in a number of Ways for The abovecompounds are best prepared by reacting in: mpl y excessive r p g of theemulsion, y Storage aqueous solution and in a mildly alkaline mediunifof the light sensitive element at elevated temperatures and 9 cysteine hd hl id i h a h l humidity, y Prolonged development f the exposedaliphatic acid such as chloroacetic acid, bromoacetic acid,emulsiohiodoacetic acid, B-bromopropionic acid or 'y-bromobutyric Agreat number 0 ahtifeggihg and Stabilizing agents acid in the presenceof an acid binding agent such.as have been recommended in the literaturefor the purpose sodium hydroxide, potassium hydroxide or h hk Aft 0f.Preventing the formation of fog in light sensitive standing for severalhours, the S-carboxyalkyl-cysteine Silver halide emhleions- Althoughthese compounds have precipitates from the reaction mixture.Alternatively, the the ability to control fog during manufacture, aswell as s ik li c l h prepared ng. during Storage, y also have distinctShortcomings to the procedures described in J. Biol. Chem. Soc., vol;For instance, they lower the sensitivity of the emulsion 106, pages331.341; J .A C.S., vol. 66, pages 1757-9, and either immediately orunder storage conditions, thus caus- 1 Chin Aota, 1 27,. 12304; ihgSpeed l'egfession- The S-carboxyalkyl-cysteine thus formed may be convWe have new found that the s-earhexyalkyl-eysteines, verted to its saltby reacting it with a Water soluble their salts and esters are excellentstabilizers and antiaihaii compound containing the d i cation such-asfoggants for silver halide emulsions having the ability to potassium b tsodium carbonate, ammonium car: maintain the sensitivity and fog at orclose to initial optihohato or the like or with a suitable acid such ashydro, mum values under keeping conditions of high temperature hl iacid, hydrohromio id and the l l and humidity i 40 If the esters aredesired, they may be producedinthe use of P compounds to lhhlhlt fog andto conventional manner by refluxing the free acid with the bilize silverhalide emulsions either by location of the desired alcohol Such asmethyl alcohol, ethyl alcohol, same in the emulsion, in layers adjacentto the emulsion h i l h l or ith a phenol in the presence of hydroor inprocessing baths for the emulsion constitutes the ohiorio id, Th.diesters. are prepared by reacting Purposes and Objects of the Presehlfihvehhohcysteine with the ester of a halogen substituted aliphatic Thes'carboxy'uower)'alkyhcystelhes, the use of which acid followed bytreatment with an alcohol in an 'acid is contemplated herein, may berepresented by the folmedium to insure complete t -ifi ti lowlhgformula: Beneficial eifects and fog reduction are obtained WhertR00CGH.OH2S(GH2)..COOR aqueous or alcoholic solutions of theaforementioned NHR1 compounds are incorporated in the silver halideemulsions as ripening finals or as coating finals. Ripening' finals areadded during the ripening or the sensitivity increasing stage of theemulsion making process. Such additions may be made before, during orafter the decomposition of the soluble silver salt such as silvernitrate bymeans of a soluble halide such as potassium-bromide, sodiumchloride or the like in the presence of ja colloidal carrier such asgelatin, PVA, solubilized casein or albumen.

Coating finals are added to the emulsion justlprior. to coating on asuitable support such as glass, paper or film at a time when theemulsion has nearly obtainedits maximum sensitivity. L I When used asripening finals, the antifoggants are best, BF 6 employed in aconcentration of 0.20 to -2.5 milligrams per mol of silver halide andwhen used as coating finals in a concentration of 0.2 to 10 milligramsper mol ofsilver halide. The concentration used depends on the ammoniumsaver or orgamc amine salts type of emulsion employed, and it isadvisable to de- -CH2SCHrCH2-COOH 7 termine the optimum concentrationfrom case to case, 7 In some instances, it is advantageous to applytheantiwherein R is hydrogen, an aliphatic radical such as lower alkyl,i.e. methyl, ethyl, propyl, butyl, amyl and'the like; hydroxyalkyl,i.e., hydroxymethyl, hydroxyethyl and the like; carboxyalkyl, i.e.,carboxymethyl, carboXyethyl and 5 like; aralkyl such as benzyl,phenethyl and thelike; or a salt forming group, i.e., sodium, potassium,ammonium, silver, tr'iethylamine, diethylamine, triethanolamine and thelike; R is a hydrogen atom, an acyl radical, i.e., 6o acetyl, proponyl,butyryl, benzoyl, phenacyl, and the like; and n is a whole number offrom 1 to 3.

Examples of compounds within the ambit of such a S-carboxymethylcysteineand its sodium, potassium,

foggant and stabilizers in layers adjacent to the emulsion, that is, ina separate undercoating layer or in the anti-abrasion gelatin surface.In other instances, the dsir e' d' res'ult may be obtained addition oilthe antifoggant and stabilizer to one or several processingbaths?s'iichas developer, prebathor the like. r

The aforesaid antifoggants and stabilizers may'be. uti lized inconnection with any type oiphotographic emulsion, e.g., non-sensitized,orthochromatic, panchromatic, boil type emulsions, ammonia typeemulsions, X-ray emulsions, paper emulsions, color emulsions or thelike. They may be employedincombinationwith'other known antifoggants andstabilizers, reductionand metal and noble metal sensitizers, or incombination with hydroxypolyethenoxy derivates, i.e., those obtained byreacting ethylene oxide with an alcohol, phenol,. amine or the. like(see US. Patent 1,970,578).

Although our stabilizers are somewhat related to cysteine, cystine andmethionine which were previously recommended as emulsion. additives,these compounds provide eve n l'mder optimum conditions only a limitedantifogging protection. 'Ihese moderate benefits are accompaniect by anumber of undesirable properties, such as reduced sensitivity of. theemulsion and. lowered. contrastv together with increased fogunderconditions of. high-temperature storage. The compounds of ourinventionare free from these disadvantages.

I The. invention is illustrated by the following examples, limit is tobe understood that the invention. is. not restficted thereto.

" Example I A-silver halide emulsion in gelatin containing 4 percentsilver iodide and 96 percent silver bromide waspre-- pared inaconventional manner and brought up to its maximumlight sensitivity. It.was then readied for coating, finals were added such as'sensitizingdyes,stabilizers and hardening. agents. A 1 percent solution. ofS'-(flcarboxyethyl)-cysteine was added to the emulsion as: anantifoggant. The. emulsion samples. weighed one kilogram and containedabout .4 mol of silver halide. The so prepared emulsion samples werecoated on a suitable cellulose ester base and dried. Samples of thesefilm: coatings were; then exposed in .a Type: IIB Sensitometer anddeveloped in a developer of the following composi- 4 precipitates were.combined. and purified by recrystallization from water. The productmelted at 192 C. The product had the following formula:

HO 0 o-on.onzs-onz-onzo 0 on NH: Ananalysisgavethe following'results:

o i H. N r s 5. be 7. s2 17. 88 5. 24 7- 68 17. 51

Example II The procedure was the same as in Example I except- Theprocedurewas the same as in Example I except that theS-(fi-carboxyethyl)-cysteine was replaced by an equivalent quantity ofN-acetyl-S carbethoxymethyl cysteine ethyl ester. The results weresimilar to those of Example I. This product was prepared according tothe procedure; described in Helv. Chim. Acta, vol. 27, pages 1280-4, 'byreacting cysteine hydrochloride in an alkaline'medium successively withchloroacetic acid and acetic anhydride and esterifying the resultantdicarl'aoxylic acid.

' Example IV The procedure was the same as in Example I except ing thatthe S -(fi carboxyethyl)cysteine was replaced by an equivalent quantityof. N-acetyLS-(fl-carboxyethyllcysteine; The. results were. similar tothose obtained in. Examplel.

Example V The antifogging action of S-(B-carboxyethyl') -cysteine wascompared with-that of cysteine and cystine. The following results wereobtained.

It is 'evident from this .table that the s-(flrcarboxyv ethyl):-cysteinereduces fog without loss .of speed. to a;

tionz;

p Grams Metol (p-methylaminophenol sulfate) L5 sulfite, anhydrous 45blSlllfite j Hydroquinone 3: carbonate, monohydrated 6 Potassium bromide7 0,8 Water to make 1 liter.

V j .Speedi LOven'fQg' Quantltyofflompoundadded Relative Fog at afteroven atfiDe- .Speed 6' Dev test velopment- TheS-(fl-carboxyethyl)-cysteine was prepared as follows: a I

15.7 grams. cysteine hydrochloride (.0.1' mol) was added to100-milliliters of 110 N sodium-hydroxide solution and the pH adjustedtoa point between 8' andf9. To this dispersion was added a solution of15.3 grams of j3- bromo-propionic acid in St) milliliters of waterwhereupon greater extent than the cysteine and the cystine which. inaddition .to: their poorer antifogging performance, cause .aserious lossof speed.

Example VI A gelatin solution containing 30 grams of gelatin, 1 0.0mgLof S'(fi carboxyethyl)cysteine per liter was coated on filmbasein' amanner known to the art. After the coating was performed,.a silverhalide emulsion in gelatin containing 4 percent of silver iodide and 9-6percent of silver bromide was coated on top of the previously coatedgelatin layer; After drying, film samples. were exposed and processed asdescribed in Example III. The samplm exhibited a relative speed of and afog of 0.12 compared with a type coating of the same emulsion havingundercoating similar to that described above, but

lacking the antifoggant and having a speed of 100 and a fog of 0.20.

Example VII Exposed samples of a photographic film were developed fortwelve minutes at 65 F. in a standard metol-hydroquinone developer. Twotests were made, one with the normal developing solution and one with adeveloper containing mgs. of S-(B-carboxyethyl)-cysteine per liter ofdeveloper. Sensitometric strips, developed in the normal developer(control) for twelve minutes, showed a fog of .30, whereas those stripswhich were developed in the developer containing the antifoggant had afog of .20.

Various modifications of the invention will occur to persons skilled inthe art. Thus, it is understood that in lieu of using the particularantifoggants of the examples, any of the antifoggants listed in theapplication may be employed with equivalent results. We, therefore, donot intend to be limited in the patent granted except as necessitated bythe prior art and the appended claims.

We claim:

1. A light sensitive photographic material comprising a base and a lightsensitive silver halide emulsion, said light sensitive materialcontaining as an antifoggant a compound of the following constitution:

wherein R is selected from the class consisting of hydrogen, and alkyl,hydroxyalkyl, carboxyalkyl, aryl and aralkyl radical and a sodium,potassium, ammonium, silver and an amine cation; R is a member selectedfrom the class consisting of hydrogen and acyl groups wherein the totalnumber of carbon atoms in said radicals and groups does not exceedeight, and n is a whole number ranging from 1 to 3. i

2. The article as defined in claim 1 wherein the antifoggant is locatedin the silver halide emulsion.

3- T e a s s s in c m 1 w ere t e ant foggant is located in a layeradjacent to said silver halide emulsion layer.

4. A light sensitive photographic material comprising a base with alight sensitive silver halide emulsion thereon, said emulsion containingas an antifoggant the compound S-(fl-carboxye'thyl) -cysteine.

5. A light sensitive photographic material comprising a base with alight sensitive silver halide emulsion thereon, said emulsion containingas an antifoggant the compound S-(carboxymethyl)-cysteine.

*6. The process of minimizing and preventing fog in light sensitivesilver halide materials comprising a base having a light sensitivesilver halide emulsion thereon, which comprises exposing said emulsionto light and developing the same in the presence of an antifogganthaving the following structural formula:

wherein R is selected from the class consisting of hydro gen, an alkyl,hydroxyalkyl, carboxalkyl, aryl and aralkyl radical and a sodium,potassium, ammonium, silver and an amine cation; R is a member selectedfrom the class consisting of hydrogen and acyl groups wherein the totalnumber of carbon atoms in said radicals and groups does not exceedeight; and n is a whole number ranging from 1 to 3.

7. The process as defined in claim 6 wherein the antifoggant isS-(B-carboxyethyl)-cysteine.

8. The process as defined in claim '6 wherein the antifoggant isS-carboxymethyl-cysteine.

References Cited in the file of this patent UNITED STATES PATENTS2,363,777 Downing et al. Nov. 28, 1944 2,438,716 Mueller Mar. 30, 19482,449,153 Urbach Sept. 14, 1948

1. A LIGHT SENSITIVE PHOTOGRAPHIC MATERIAL COMPRISING A BASE AND A LIGHTSENSITIVE SILVER HALIDE EMULSION, SAID LIGHT SENSITIVE MATERIALCONTAINING AS AN ANTIFOGGANT A COMPOUND OF THE FOLLOWING CONSTITUTION: